Field of the Invention
The invention relates to a fuel tank for a motor vehicle.
Description of the Background Art
According to conventional practice, fuel tanks can be produced from a thermoplastic resin, for example by extrusion blow molding or by welding injection-molded half-shells made of thermoplastic resin. In the interior of such a fuel tank, functional components of the fuel system can be accommodated, as a result of which the space requirement outside the fuel tank is reduced and, in addition, the number of required tank openings is reduced, which is advantageous with regard to emissions from the fuel tank.
DE 102 60 953 A1, which corresponds to US 2004/0129708, discloses a generic fuel tank which is designed as a blow-molded hollow plastic member. In its interior, a functional component support is inserted, to which various functional components, such as a fuel pump, a level indicator or valves, are attached. The functional component support can be a planar baffle wall, by means of which surge movements of the fuel can be reduced during vehicle operation. In addition, the functional component support has strut arrangements, which are spaced apart from one another, of which the supporting legs are supported on opposite inner sides of the fuel tank wall.
In the production of the fuel tank, the functional component support is first fitted with the functional components by forming a pre-assembly unit, which is separate from the fuel tank. The assembled functional component support is then inserted into the interior of a tubular fuel tank preform made of thermoplastic resin. Subsequently, a blow molding process takes place, in which the preform is expanded to its final outer contour in a blow molding tool using blown air and application of heat. During the blow molding process, the functional component support is also welded or glued to the inside of the fuel tank in the region of its supporting legs. At least the supporting legs of the functional component support are made of a plastic material, which is compatible with the plastic material of the fuel tank with regard to weldability.
A rigid connection of the functional component support to the fuel tank is of great importance in order to ensure the functional reliability of the functional components even in extreme driving situations, such as an extreme curve position or an extreme acceleration. The functional component support must therefore be rigidly connected to the fuel tank by means of the supporting legs so as to ensure a torsion-proof, tilt-proof and non-slip positioning in the fuel tank. For such a rigid connection, the functional component support has the abovementioned strut arrangements, which are supported in the installation position between the opposite fuel tank walls.
Due to different conditions, for example temperature fluctuations, pressure fluctuations, component tolerances, material shrinkage, exposure of the vehicle/mechanical action from outside, the fuel tank can change its shape or size. In the case of a rigid connection of the functional component support to the fuel tank, this can produce mechanical component stresses between the fuel tank and the functional component support. The component stresses may have an effect on the functional component carrier, leading to damage to the functional components.